1. Field of the Invention
The present invention relates to a starter and, more particularly, to a so-called overhang type starter in which a pinion is provided at a portion ahead of a bearing.
2. Description of the Prior Art
A typical conventional starter of the type described above has heretofore been constructed as shown in FIG. 3. In the FIG., the reference numeral 1 denotes a rotary output shaft which is connected to an armature rotary shaft 2 of an electric motor through an epicyclic reduction gear (not shown). Formed in the periphery of the output shaft 1 is a helical spline 3 with which an overrunning clutch 4 is spline-fitted for axial sliding in relation to the output shaft 1. The numeral 5 denotes an outer member of the overrunning clutch 4 the inner surface of which is provided with a spline-fitting portion 5a which is in fitting engagement with the helical spline 3. The numeral 6 denotes a clutch inner member which is formed integral with a driving shaft 8 which has a pinion 9 provided on its front end portion. The numeral 7 denotes a roller which is interposed between the outer and inner clutch members 5 and 6. The reference numeral 10 denotes a bearing which is firmly press-fitted into a front bracket 11 serving as a machine frame of the starter and which slidably supports the driving shaft 8. The numeral 12 denotes a pinion stopper which is provided on the front end portion of the output shaft 1, 13 a ring for securing the stopper 12, and 14 sleeve metal members provided between the output shaft 1 and the driving shaft 8. Futher, the reference numeral 15 denotes a lever which is pivotally installed with one end thereof engaged with a plunger 17 of an electromagnetic switch 16 and the other end thereof engaged with the overrunning clutch 4.
The operation of the starter having the above-described arrangement will next be explained.
When a starting switch (not shown) is turned on, the electromagnetic switch 16 is energized and the plunger 17 is thereby magnetically drawn and then the lever 15 pivots counterclockwise, thus causing the overrunning clutch 4 to move forward. In consequence, the driving shaft 8 moves forward to bring the pinion 9 into engagement with a ring gear (not shown) of an internal combustion engine. The output shaft 1 is rotated by the electric motor through the epicyclic reduction gear and the rotation of the output shaft 1 is transmitted through the overrunning clutch 4 to the driving shaft 8, that is, the pinion 9 formed thereon, thereby starting the engine. The forward movement of the driving shaft 8 is restricted by the pinion stopper 12 so that the pinion 9 is prevented from projecting excessively from the front end of the front bracket 11.
The conventional starter having the above-described arrangement suffers, however, from the following problems. Since the driving shaft 8 is supported by the bearing 10, when the shaft 8 is advanced or projected (as can be seen from the lower side of the output shaft 1 in FIG. 3), the point at which the shaft 8 is supported by the bearing 10 shifts rearward relative to the pinion 9, that is, the amount of overhang of the pinion 9 increases, and therefore deflection of the output shaft 1 becomes correspondingly serious. Accordingly, when the pinion 9 is rotating, the bearing 10 and other portions are load-bearing, so that it is difficult to obtain desired characteristics and the durability of the starter is disadvantageously low.